(Field of the Invention)
The present invention relates to a structure of a toroidal continuously variable transmission.
(Description of Related Art)
As an electric power generating device for an aircraft, it is known to use a constant frequency generator (IDG) that operates while keeping a rotation rate (frequency) of a generator constant even when a rotation rate of an aircraft engine, which is a drive source, varies. As a transmission for keeping a rotation rate of the generator constant in the IDG, a toroidal continuously variable transmission has been proposed. The toroidal continuously variable transmission includes a toroidal transmission unit that includes: an input disc and an output disc concentrically arranged so as to be opposed to each other; and a power roller that is brought into contact with opposed curved concave surfaces of both discs at high pressure. By adjusting a tilt angle of the power roller relative to both discs, it is possible to steplessly (continuously) vary a gear ratio (see, e.g., Patent Documents 1 and 2).
In general, the discs of the toroidal continuously variable transmission are rotated at a high speed. Thus, when the discs are unbalanced even slightly, there is a possibility that large whirling occurs, so that it is necessary to correct the unbalance of the discs. As a technique to correct the unbalance of the discs of the toroidal continuously variable transmission, use of the outer peripheral surface, at the radially outer side, of each disc as an unbalance correction surface, for example, by performing processing such as perforating the outer peripheral surface, or by fixing a balancing ring to the outer peripheral surface, has been proposed (see Patent Document 3).